Prior art systems for testing electronic devices, and in particular, for testing semiconductor devices typically include electronic circuits, a frame, and a manipulator assembly which attaches to a testing head. The electronic circuits for testing are located in the test head itself. However, some electronic circuits for processing and recording the testing may be located within the frame or within a separate computer. A cable assembly consisting of multiple cables is used to provide power to the electronic circuits of the test head and to connect the electronic circuits in the test head to utilities such as power sources and to other devices. Since the testing process requires a large amount of power, large, heavy power cables are required to transfer the power from the power source to the test head. Testing units that do pressure testing include cables that couple high pressure gas from a source to the test head. In addition, due to the heat generated by the complex processing circuitry in the test head, the test head must be cooled. One way to cool the electronic components in the test head is to circulate cooling fluids through the test head. In testing devices that circulate cooling fluids, cables conduct the cooling fluid from a heat exchanger to the test head and return the spent cooling fluid to the heat exchanger. In prior art systems, the cable is commonly left lying on the ground or held up by slings as it extends from the manipulator assembly to the processing circuitry.
Prior art manipulator assemblies use yokes which attach to opposite sides of a testing head for producing tumble motion in the test head. Though these prior art manipulator assemblies do allow for some motion, the range of motion is quite limited. In addition, the yoke gets in the way, obstructing the operators access to the testing surface and limiting the movement of the test head itself.
More recent manipulator assemblies typically allow for horizontal motion by attaching an arm to a vertical rail. The arm attaches to the testing head using a yoke that attaches to opposite sides of the testing head. The yoke must be large enough to allow the testing head to fit within the interior of the yoke and it must be strong enough to support the heavy weight of the testing head. Consequently, designs that use yokes are bulky due to the large diameter of the yoke and the large size of the yoke.
Prior art testers take up a significant amount of room on the assembly room floor. In addition, due to the heavy weight of testing devices, the devices are difficult to move. Based on the layout of the assembly room and the equipment used in the assembly and handling processes, prior art systems have been designed to fit within specific locations and to perform testing within narrowly defined criteria. Thus, testers are generally custom designed to fit the needs of particular users.
As products have rapidly matured and assembly and handling equipment has been updated, the narrow range of movement and lack of flexibility of prior art designs has prevented many designs from fitting into the workspace area allocated for testing equipment. In addition, as assembly methods and wafer handling methods have become more automated and sophisticated, users are requiring different criteria and ranges of motion. Moreover, the test head must interface with a large loader. There are many different loader manufacturers and a variety of different loader designs. Therefore, the test head must be moved into various positions to accommodate the particular design of each loader used in the manufacturing process. Typically, prior art manufacturers have simply added new models which meet each new criteria or they modify existing designs to accommodate the needs of a particular customer. This process is time consuming and expensive. In addition, it results in a testing device which may need to be modified whenever a user purchases different handling equipment or changes the assembly room layout.
Space on the assembly room floor is limited and expensive. Testing devices compete for space with other devices such as handlers and probers which must be used in close proximity to the tester. Therefore, footprint and versatility of use for testing devices is critical.
More recent designs have increased the versatility of the tester's design by allowing for vertical motion of the manipulator. These prior art testers include manipulator assemblies that have a vertical rail system for positioning the manipulator. The vertical rail is typically a short round rail around which a horseshoe shaped attachment fitting resides. The attachment fitting is typically attached to an arm which is attached to one end of the yoke. The testing head is then attached to the yoke. A locking screw allows the arm to be moved up and down along the length of the vertical rail until the testing head is properly positioned and then engaged so as to lock the testing head into the proper position. However, the range of vertical motion is typically limited to 26 to 28 inches of vertical motion. Thus, these types of prior art testers, though they are more versatile than other prior art designs, still only offer a narrow range of improvement.
Other recent design improvements have included the use of pivots that are placed between the portion of the arm that attaches to the frame and the yoke so as to allow for the movement of the yoke within a radial arc around the pivot point. Though this type of design allows for more versatility it still does not accommodate the needs of many loader designs and different assembly room layouts. In particular, some loaders require testing with the test head forward which is typically referred to as device under testing (DUT) forward. Other loaders require testing in the DUT up position (where the device to be tested is placed over the test head) and the DUT down position (where the device to be tested is placed below the test head). For these applications, though prior art manipulators may pivot, they still must be specifically designed for each required testing position as dictated by the loader used and the layout of the testing area.
Yet another recent improvement has been the incorporation of "twist" motion into the manipulator design. Prior art designs which allow for "twist" incorporate rotary bearings between the connection to the pole and the arm. By rotating the bearings, the arm, the pivot, the yoke and the test head rotate. This design allows DUT up, DUT down and DUT forward testing to be performed by the same testing unit without the need to reconfigure the testing device itself. However, the heavy cables make movement difficult and limit the range of movement. In addition, the cables prevent the tester from being moved into various positions as they interfere with pivoting, rotation and tumble movement. Moreover, prior art designs using yokes have little or no tumble motion. This is because the yoke design, in combination with the heavy cables, allows only a limited amount of movement of the test head within the yoke. Typically, movement of the test head within the yoke is only plus or minus two and a half inches along the outer edges of the test head.
Since the length of the manipulator is fixed only motion within a fixed arc is possible. Thus, though prior art designs allow for twist, pivot, up, down and minimal tumble motion, the range of motion is limited to a fixed arc. Only those testers that allow for horizontal motion provide for movement outside of a single horizontal arc. However, since horizontal motion of prior art manipulators is typically only eight inches or less, the range of movement provided by manipulators with horizontal motion is still quite limited.
The yoke, the arm, the cable and the test head are relatively heavy. The weight of these components causes the arm on prior art designs to deflect. This deflection is commonly referred to as sag. This sag causes misalignment at the testing head that often cannot be corrected by the up and down motion, pivot motion, twist motion or even the limited tumble motion of prior art manipulators. The limited tumble motion allowed by prior art tester designs can correct for sag when the amount of sag is small enough to be corrected by the limited tumble movement allowed by the yoke design. However, sag correction using the limited tumble motion of the yoke is only possible for a few testing positions and correction is dependent on the orientation of the yoke. Some test heads allow for rotation of the testing surface with respect to the test head. However, this motion is limited (usually no greater than a total movement of 3 degrees). In some cases, this correction is not sufficient to overcome the deflection of the arm. In addition, since the movement of the electronics within the test head moves the electronics package out of the locked position. When the electronics package is moved out of the locked position, the electronics package may rotate within the test head. This freedom of movement of the electronics package within the test head may cause damage to the delicate electronics located within the electronics package due to motion, vibration and shock to the test head. Therefore, movement of the testing surface is not a good solution to the problem of sag correction.
Accordingly, what is needed is a tester design which includes a manipulator that has a limited footprint and which will allow for a full range of movement of the test head. More specifically, a manipulator which is not restricted to movement within a radial arc is needed. Furthermore, a tester design which will allow for the compensation of sag is needed. In addition, a tester design which will allow for full "tumble" movement is needed. Moreover, a design which will allow for smooth and easy adjustment and positioning of the test head is required. The present invention provides such solutions to the above needs.